How to add a New User to SharePoint Group using Powershell Script

Steps

1. Start your windows PowerShell on your computer.
2. Right click and select Run as administrator option.
3. Paste the below script on the PowerShell window and click the enter button.
4. Check your SharePoint site Feature will activated successfully.

if ((Get-PSSnapin "Microsoft.SharePoint.PowerShell" -ErrorAction SilentlyContinue) -eq $null)
{
    Write-Host "Connect Sharepoint cmd-Let"
    Add-PSSnapin Microsoft.SharePoint.PowerShell
}

$url = "http://gauti.sharepoint.com"
$site = new-object Microsoft.SharePoint.SPSite($url)
$web = $site.OpenWeb()
$groups = $web.sitegroups

$userName = "username\Domain"
write-host "--------------"
$i = 0;
$myGroups = @();
foreach($group in $groups) {
  if($group -match "admin")
    {
        $myGroups += $group
    }
}

foreach ($gr in $myGroups)
{
    write-host $gr
#add user to SP Group
    Set-SPUser -Identity $userName -web $url -Group $gr
    $theGroup = $web.SiteGroups[$gr]
    $theUser = $web.AllUsers.Item($userName)

#Remove user from SP Group
#   $theGroup.RemoveUser($theUser);
    write-host "User " $userName   "added to " $gr
}

Run the script with the required administrator privilege.To verify that, go the group chec user added or not.

Thanks For reading.